Heat exchangers

Abstract

A method of making a heat exchanger consisting of a conduit having a plurality of passes joined by integral return bends which comprises (i) bending two strips of material together in a zigzag manner to form a stack of substantially parallel passes, the two strips being displaced laterally with respect to one another, (ii) bonding the two strips together along lines substantially parallel to their longitudinal edges to form a flat, serpentine conduit, and (iii) inflating the conduit by applying internally a fluid under pressure.

I claim: 
     
       1. A method of making a heat exchanger consisting of a conduit having a plurality of passes joined by integral return bends which consists essentially of, in sequence, (i) bending two strips of pliable material together in a zigzag manner to form a stack of parallel passes, the two strips being displaced laterally with respect to one another,   (ii) bonding the two strips together along lines parallel to their longitudinal edges to form a flat, serpentine conduit, and   (iii) inflating the conduit by applying internally a fluid under pressure.   
     
     
       2. Method according to claim 1, in which the strips are of metal. 
     
     
       3. Method according to claim 2, in which the strips are of aluminum or aluminium alloy. 
     
     
       4. Method according to claim 1, in which the strips are from 0.01 to 0.8 mm thick. 
     
     
       5. Method according to claim 1, in which the passes in the inflated conduit are parallel. 
     
     
       6. Method according to claim 1, in which the two strips are displaced laterally with respect to one another by being (a) folded together and then pulled apart in the direction at right angles to the height of the stack, or   (b) folded separately to the same dimensions and fitted together so that the folds almost coincide, or   (c) folded together in the required displaced configuration.   
     
     
       7. Method according to claim 1, in which the longitudinal edges of the strips are bonded by means of an adhesive. 
     
     
       8. Method according to claim 7, in which the adhesive is a thermosetting resin adhesive composition. 
     
     
       9. Method according to claim 2, in which the longitudinal edges of the metallic strips are bonded by welding, soldering, or brazing. 
     
     
       10. Methods according to claim 1, in which packing pieces, each twice the thickness of the strips, are inserted between each pair of passes in the return bends and pressure is applied to assist the bonding of the two strips together. 
     
     
       11. Method according to claim 1, in which the conduit has two or more separate channels. 
     
     
       12. Method according to claim 1, in which the conduit has two or more interconnecting channels. 
     
     
       13. Method according to claim 1, in which shaped tool pieces are inserted between layers of conduit, and the stack is constrained within a frame and fitted between tie bars before the conduit is inflated. 
     
     
       14. Method according to claim 1, in which finning pieces are inserted between passes of conduit before or after inflation. 
     
     
       15. Method according to any of claim 1, in which the heat exchanger is provided with a coating.